Fluid centrifuge



May 15, 1962 R. CARMON ETAL 3,034,570

FLUID CENTRIFUGE Filed Sept. 25, 1958 5 Sheets-Sheet 1 May 15, 1962 R. L. CARMON ETAL 3,034,570

FLUID CENTRIFUGE Filed Sept. 25, 1958 3 Sheets-Sheet 2 www@ H TTOP/Vfy May 15, 1962 R. I.. CARMON ETAL. 3,034,570

FLUID CENTRIFUGE Filed Sept. 25, 1958 5 Sheets-Sheet 5 4 5 5d C l/- L ,50

United States Patent 3,034,570 FLUID CENTRIFUGE Richard L. Carmon and Francis R. Rogers, South Bend,

Ind., assignors to The Bendix Corporation, a corporation of Delaware Filed Sept. 25, 1958, Ser. No. 763,407 13 Claims. (Cl. 15S-36.4)

This invention relates generally to apparatus for removing particles of foreign material from a uid and particularly to a fluid centrifuge.

In many hydraulically operated servo systems it is desirable to provide a source of pressurized fluid which is maintained free of particles of foreign material such that plugging of valve orifices, excessive wear of precision mechanical surfaces, and sticking of sliding members is eliminated. One such servo system may be found in almost -any conventional jet engine fuel control system and, preferably, it is with such a fuel control system that the present invention is designed for use.

Heretofore, the particles of foreign matter have been removed from the pressurized fluid by means of relatively tine mesh lter screens which are subject to clogging due to the gradual accumulation of particles of matter on the external surface of the filter screen. This requires frequent removal and cleaning or replacing of the filter screen if the eiciency of the lilter is not to be impaired. It is, therefore, an object of this invention to provide a uid centrifuge for removing particles of foreign matter from a fluid.

It is an object of this invention to provide a fluid centrifuge which is simple in construction, easy and economical to make and ecient in operation.

Another object of this invention is to provide a lightweight and compact fluid centrifuge.

It is a further object of this invention to provide means for removing foreign particles of matter from a fluid which functions indefinitely without the need for periodic e cleaning.

Another important object of this invention is to provide a fluid centrifuge which requires no moving parts for its operation.

Additional objects and advantages of the present invention will be apparent to those skilled in the art from the following description and accompanying drawings, where- FIGURE 1 is a schematic representation of a fuel system embodying the present invention;

FIGURE 2. is a schematic representation of the duid centrifuge embodying the present invention;

FIGURE 3 is a sectional View taken on line 3 3 of FIGURE 2;

FIGURE 4 is a sectional view taken on line 4-4 of FIGURE 3;

FIGURES 5 and 6 are views similar to FIGURE 4, showing modifications of the pipe 56;

FIGURE 7 represents a sectional view taken on line 7-7 of FIGURE 5;

FIGURE 8 represents a view similar to FIGURE 7, showing a modification of the port 64;

FIGURE 9 is a schematic representation of a modified form of the present invention; and

FIGURE l0 is a plan view of the modified form shown in FIGURE 9.

Referring to the drawings, numeral 10 indicates a fuel conduit which receives fuel from a fuel tank 12 and disice charges fuel to a combustion engine, not shown. An engine driven fuel pump 14 is provided to pressurize the fuel in the fuel conduit 10. A variable area orice 16 disposed in conduit 10 serves to control the 'flow of fuel through conduit 10. The effective ow area of the orifice 16 is controlled by a valve 18 connected to a servo piston 20 which slides in a chamber 22. The servo piston 20 divides the chamber 22 into two variable volume chambers, 24 Vand 26, which are connected to a servo supply passage 30 via passages 32 and 34, respectively. A restriction 36 is secured in passage 32. The pressure drop across the servo piston 20 and thus the position of the piston is controlled by a liapper valve 38 which coacts with a valve seat 40 at the outlet end of a passage 42 connected between the chamber 24 and a suitable source of drain pressure Po, not shown. The apper valve 38 is connected to one end of a rod 44, the opposite end of which is connected to control apparatus 46. The control apparatus 46 is responsive to one or more variable conditions of engine operation such as speed, temperature and the like and produces an output signal by means of which the rod 44 and thus apper valve 38 are actuated as a `function of the variable conditions 0f engine operation. The control apparatus 46 is conventional in operation and does not form any part of the present invention.

A fluid centrifuge 48 is arranged to receive fuel under pressure from conduit 10 via an inlet passage 50 and discharge a portion of the lfuel received to servo supply passage 30. The remaining portion of the fuel received is discharged to conduit 10 via an outlet passage 52. A pressure relief valve 54 of any known convenient type is disposed in conduit 10 between inlet passage 50 and outlet passage 52. The pressure relief valve 54 is responsive to the pressure drop across the fluid centrifuge 48 and functions to direct the total output of pump 14 to the lluid centrifuge 48 until said pressure drop reaches a predetermined value at which time the valve 52 opens to allow the excess fuel to ow therethrough to valve 18.

Referring to FIGURE 2, wherein the fluid centrifuge 48 is shown schematically in greater detail, numeral 56 designates a pipe having an vinlet end 58 and an outlet end 60 connected to inlet passage 50 and outlet passage 52, respectively, via suitable pipe couplings 62. The pipe 56 is spirally coiled about a central axis and in its preferred congurationforms a helical ow path which decreases in diameter in the general direction of fuel flow from inlet passage 50 to outlet passage 52. The pipe 56 is of uniform cross-sectional ow area throughout its length. At the smallest diameter of the spiral, the inner Wall of the pipe 56 is provided with one or more openings or ports 64 radially formed therein (see FIGURE 3) which open into the interior of a semi-round receptacle 66. The receptacle 66 has an opening 68 circumferentially formed in the Wall thereof which encircles the opening or port 64. The receptacle 66 and pipe 56 are xedly secured together by any suitable means such as a weld which provides a fluid seal. Centrifuged fuel collects in the receptacle 66 in a mannerAto be explained and is extracted therefrom via an outlet port 69 formed in the end wall of the receptacle 66 thereafter flowing to the servo supply passage 30 via a passage 70 connected between the outlet port 69 and the supply passage 30.

Fuel flowing through the pipe 56 is acted upon by centrifugal force which causes particles of foreign matter carried by the fuel to move outwardly in the pipe away from the axis of the spiral. The centrifugal force which 3 acts on any given particle of foreign matter varies in accordance with the relationship v2 Fn: m-

where Fc represents the centrifugal force, m the mass of a given particle of matter, v the linear or tangential velocity of the given particle of matter at a given point in the flow stream, and r the radial distance from the central axis of the spiral to the center of gravity of the particle of matter. Since the pipe 56 has a uniform cross-sectional flow area throughout its length the linear or tangential velocity v of a given particle of matter remains substantially constant throughout its travel through the pipe 56, assuming a constant pressure drop at all times across the centrifuge 48, as will be appreciated by those familiar with the fundamentals governing the ow of incompressible uids through pipes. For a given particle of foreign matter the mass m is constant. Therefore, it is readily seen that the centrifugal force Fc acting on a particle of foreign matter having a given mass m varies as a function of the radial distance r only. Thus, the centrifugal force which varies as an inverse function of the radial distance r progressively increases as the diameterV of the spiral decreases vand reaches a maximum value in the region of the opening or port 64. It will be realized that, by virtue of Vtheir different densities and settling rates, particles of lint, sand and metals which ordinarily make up the bulk of contaminants in a lfuel supply will respond to the centrifugal effect to varying degrees. Y

Referring to FIGURE 4 which represents a cross section of pipe 56 taken on line 4--4 of FIGURE 3, the cross-sectional area of the pipe 56 is divided into two portions. The innermost one-third portion represents fuel from which the particles of matter have been displaced and the remaining two-thirds represents fuel to which the particles of foreign matter have been displaced. Thesymbol d represents the maximum distance along a radial line that a particle of foreign matter must be displaced during its travel through pipe 56 to escape the innermost onethird portion of the flow path. The length of the pipe 56 is dependent upon the particle of matter having the least density and corresponding lowest settling rate and the distance d through which it is to be displaced, and must be long enough to meet the time requirement imposed by these Variables. FIGURES 5 and 6 represent rectangular and elliptical versions of pipe 56 which are designated by numerals 56a and 56b, respectively. The pipes 56a and 56b have rectangular and elliptical flow areas, respectively, Yeach of which are divided into two areas equivalent to the corresponding two areas of the circular pipe 56 shown in FIGURE 4. It will be noted that while the area remains the same in all cases ala and db is less in the rectangular and elliptical versions of pipe 56 as compared to the distance d in the circular version such that a shorter pipe may be used.

In the region of port 64, it is desirable to minimize the effects of turbulent flow which may cause some 0f the centrifuged particles of matter to re-enter the inner portion of the flow path and be carried out of the port 64. FIGURES 7 and 8 illustrate alternate means Iwhich may be provided in the pipe 56, 56a or 56b to avoid this problem. Referring to FIGURE 7, numeral 72 designates a thin plate connected at its top and bottom edges to the pipe 56a and connected at one end to the inner wall of the pipe 56a adjacent the downstream edge of the port 64. The plate 72 extends upstream of the port 64 and is spaced from the inner Wall of pipe 56a in accordance with the distance a.'a indicated in FIG- URE 5. The plate 72 acts as a flow divider and provides an effective barrier between contaminated fuel and uncontaminated fuel in the region of port 64.

Referring to FIGURE 8, turbulent flow in the region of port 64 may also be reduced by providing port 64 with curved edges which tend to divert fuel through port 64 Y from the main oW path at a relatively small angle. As

shown in FIGURE 8, the upstream edge 74 of port 64 is curved inwardly with respect to the axis of the pipe 56a and the downstream edge 76 of port 64 is curved outwardly with respect to the axis of the pipe 56a.

A predetermined minimum pressure drop is maintained across the centrifuge 48 in order to force fuel through Vpipe 56 at a rate whereby theV required linear velocity is developed to effect separation of the particles of foreign matter from the fuel in the aforementioned manner. The predetermined minimum pressure drop also serves to maintain an adequate supply of fuel to meet the fuel flow requirements of the servo system at all times. To this end, the pressure relief valve 54 operates to maintain the predetermined minimum pressure drop across the centrifuge 48 regardless of the output of pump 14 which during normal operation is considerably in excess of that required for proper centrifuge action.

During operation of the system, contaminated fuel flows from the pump 14 through passage 50 into pipe 56. As the fuel flows through pipe 56 centrifugal force acts upon the particles of foreign matter causing the particles to move toward the outermost portion of the spiral ow path in the order of their densities, the most dense responding relatively fast and the least dense responding relatively slow. As the centrifugal force increases in accordance with the decreasing diameter of the spiral flow path, the particles will be cause to settle out progressively faster such that the centrifuged particles are concentrated in the outermost two-thirds portion of the flow path by the time the opening or port 64 is reached. Theparticles of foreign matter are carried by the fuel past the opening or port 64 through passage 52 to conduit 10. Clean fuel is extracted from the innermost one-third portion of the flow path via the opening or port 64 which yempties into the receptacle 66 which in turn supplies the servo system with fuel as required.

It will be understood that the pipe 56 is not restricted to being coiled in the helical pattern shown inFIGURE 2 but may be spirally coiled in one plane, as illustrated in FIGURES 9 and l0, without reducing the effectiveness of the centrifuging action. Various other modifications of the preferred embodiment may be made by those skilled in the art within the scope of the invention as dened im the appended claims.

We claim:

1. Apparatus for separating contaminants from a pres-- surized uid, comprising a receptacle for uncontaminatedl fluid; an outlet passage for contaminated uid; a conduit. communicating said pressurized fluid with said outlet pas-- sage; said conduit being coiled about an axis and having an. outlet port formed in the radially innermost wall thereof, said outlet port communicating with said receptacle, said' uid being forced through said conduit at a rate whereby centrifugal force causes said contaminants to collect in a. portion of the fluid flowing through said conduit leaving the remaining portion relatively free of contaminants, the` latter named portion being ejected through said outlet porti to said receptacle and the former named portion together with said contaminants being discharged to said outlet: passage.

2. Apparatus as claimed in claim 1 wherein said con-- duit is a pipe having a circular cross-sectional flow area.

3. Apparatus as claimed in claim l wherein said con duit is a pipe having a rectangular cross-sectional flow' area.

4. Apparatus as claimed in claim l wherein said conduit is a pipe having an elliptical cross-sectional flow area.

5. Apparatus for separating contaminants from a pressurized uid comprising a receptacle for uncontaminated uid; an outlet passage for contaminated uid; a conduit communicating said pressurized fluid with said outlet passage, said conduit being coiled about an axis and having an outlet port formed in the wall of said conduit and communicating with said receptacle, said outlet port being upstream from said outlet passage and radially disposed in the wall of said conduit toward said axis, said iiuid being forced through said coiled conduit at a rate whereby centrifugal force causes said contaminants to move outwardly in said conduit relative to said axis leaving a portion of the fuel flowing through said conduit relatively free of contaminants, said uncontaminated fuel owing through said outlet port to said receptacle and the remaining portion of the fuel together with said contaminants flowing through said conduit to said outlet passage.

6. Apparatus for separating contaminants from a pressurized iluid comprising a receptacle for uncontaminated fluid; an outlet passage for contaminated uid; a conduit communicating said pressurized uid with said outlet passage, said conduit forming a spiral flow path which decreases in diameter in the direction of fuel ow with respect to an axis; an outlet port disposed in the wall of said conduit toward said axis; said fluid being forced under pressure through said conduit at a rate whereby centrifugal force causes the contaminants to move outwardly in said conduit relative to said axis leaving a portion of the fuel flowing through said conduit relatively free of contaminants, said uncontaminated fuel being ejected from said conduit through said outlet port to said receptacle and the remaining portion of the fuel in said conduit together with said contaminants being ejected through said conduit to said outlet passage.

7. Apparatus for separating contaminants from a pressurized fluid, comprising a receptacle for uncontaminated fluid; an outlet passage for contaminated duid; a conduit communicating said pressurized fluid with said outlet passage, said conduit being coiled about an axis so as to form a decreasing diameter helical flow path; an outlet port radially disposed in the wall of said conduit toward said axis; said uid being forced under pressure through said conduit at a rate whereby centrifugal force causes the contaminants to move outwardly in said conduit relative to said axis leaving a portion of the fuel owing through said conduit relatively free of contaminants, said uncontaminated fuel being ejected from said conduit through said outlet port to said receptacle and the remaining portion of the fuel in said conduit together with said contaminants being ejected through said conduit to said outlet passage.

8. In a fuel control system for a combustion engine having a burner, the combination of a source of fuel under pressure; a fuel conduit for delivering fuel from said source to said burner; valve means in said fuel conduit for controlling fuel ilow therethrough; fuel operated servo means operatively connected to said valve means for controlling the position thereof; means responsive to a variable condition of engine operation for controlling said servo means; and means for removing foreign particles of matter from the fuel supplied to said servo means including a fuel conduit spirally coiled about an axis, said spiral conduit having an inlet connected to receive fuel from said source of fuel and an outlet connected to discharge fuel to said first named fuel conduit upstream from said valve means, means including a valve member in flow controlling relationship with said first named fuel conduit for generating a pressure drop between said inlet and outlet connections; an outlet port disposed in the wall of said spiral conduit toward said axis upstream from said outlet and communicating with said servo means, said fuel being forced through said spiral conduit at a rate whereby centrifugal force causes the foreign particles of matter to move outwardly in said spiral conduit relative to said axis leaving a portion of the fuel in said spiral conduit substantially free of contaminants, said uncontaminated fuel being ejected from said conduit through said spiral outlet port and the remaining portion of the fuel in said spiral conduit together with said foreign particles of matter being ejected through said outlet to said rst named fuel conduit.

9. In a fuel control system for a combustion engine having a burner, the combination of means for supplying fuel under pressure in excess of engine fuel requirement; a fuel conduit for delivering fuel from said means to said burner; valve means in said fuel conduit for controlling fuel flow therethrough; control means responsive to a variable engine operating condition for controlling the operation of said servo means; pressure responsive valve means disposed in said fuel conduit in series flow relationship with said valve means; and means for removing particles of foreign matter from the fuel supplied to said servo means including a fuel conduit spirally coiled about an axis, said spiral conduit having an inlet connected to said first named fuel conduit upstream from said pressure responsive valve and an outlet connected to said iirst named fuel conduit downstream from said pressure responsive valve; and a plurality of spaced outlet ports disposed in the wall of said spiral conduit toward said axis upstream from said outlet and communicating with said servo means, said fuel being forced through said spiral conduit at a rate whereby centrifugal force causes the particles of foreign matter to move outwardly in said spiral conduit relative to said axis leaving a portion of the fuel in said spiral conduit substantially free of said particles of foreign matter, said portion of the fuel being ejected from said spiral conduit through said plurality of outlet ports and the remaining portion of the fuel in said spiral conduit together with said particles of foreign matter being ejected through said outlet to said rst named fuel conduit, said pressure responsive valve means being operative to maintain the pressure drop across said last named means above a predetermined minimum value.

10. In a fuel control system for a combustion engine having a burner, the combination of a source of fuel under pressure; a fuel conduit for delivering fuel from said source to said burner; valve means in said conduit for controlling ilow therethrough; fuel operated servo means operatively connected to said valve means for controlling the position thereof; means responsive to a variable condition of engine operation for controlling said servo means; and means for removing foreign particles of matter from the fuel supplied to said servo means including a fuel conduit coiled about an axis, said coiled fuel conduit having an inlet connected to receive fuel from said source of fuel and an outlet connected to discharge fuel to said fuel conduit, an outlet port disposed in the wall of said conduit toward said axis upstream from said outlet and communicating with said servo means, said fuel being forced through said conduit at a rate whereby centrifugal force causes the foreign particles of matter to move outwardly in said conduit relative to said axis leaving a portion of the fuel in said conduit substantially free of contaminants, said uncontaminated fuel being ejected from said conduit through said outlet port and the remaining portion of the fuel in said conduit together with said particles of foreign matter being ejected through said outlet to said fuel conduit.

1l. In a fuel control system as claimed in claim 10 wherein said means for removing foreign particles of -matter further includes valve means operatively connected to said coiled fuel conduit for controlling the ow of fuel therethrough'to maintain the pressure drop thereacross above a predetermined minimum value.

l2. In a fuel control system for a combustion engine having a burner, the combination of a source of fuel under pressure; a fuel conduit for delivering fuel from said source to said burner; valve means in said conduit for controlling fuel flow therethrough; fuel operated servo means operatively connected to said valve means for controlling the position thereof; means responsive to a variable condition of engine operation for controlling said servo means; and centrifuge means including means dening a spiral flow path operatively connected to said fuel conduit and said servo means for removing foreign particles of matter from a portion of the fuel flowing from said source, said portion of the fuel flow being delivered to said fuel operated servo means and the'remain- References Cited in the le of this patent ing portion of the fuel 110W from said source together with UNITED STATES PATENTS said foreign particles of matter being delivered to said fuel conduit. 972,282 Stamets Oct. 11, 1910 13- Apparatus as claimed in claim 6 wherein said con- 5 2,614,617 Bobier Oct, 21, 1952 duit 1S coiled spirally with substantially all of the coils in 2,719,631 Vicard Oct. 4, 1955 Aone plane. 2,940,517 Skellern June 14, 196() 

